(19)
&
EP 1 477 755 B1
(11)
EUROPEAN PATENT SPECIFICATION
(12)
(45) Date of publication and mention
(51) Int Cl.:
F25J 1/02 (2006.01)
F25B 9/00 (2006.01)
of the grant of the patent:
06.04.2011 Bulletin 2011/14
F25D 3/10 (2006.01)
(21) Application number: 04015275.3
(22) Date of filing: 30.11.1999
(54) Liquid helium recondensation device and transfer line used therefor
Vorrichtung zur Rekondensation von flüssigem Helium und dafür verwendete Transportleitung
Appareil permettant de recondenser de l’helium liquide et conduite de transfert utilisee a cet effet
(84) Designated Contracting States:
(74) Representative: Jackson, Robert Patrick
DE FI FR GB
Dehns
St Bride’s House
10 Salisbury Square
London
EC4Y 8JD (GB)
(30) Priority: 25.12.1998 JP 36906498
(43) Date of publication of application:
17.11.2004 Bulletin 2004/47
(56) References cited:
(62) Document number(s) of the earlier application(s) in
accordance with Art. 76 EPC:
99973547.5 / 1 197 716
(73) Proprietor: Japan Science and Technology
Agency
Kawaguchi-shi,
Saitama 332-0012 (JP)
US-A- 3 882 687
US-A- 4 432 216
US-A- 4 796 433
US-A- 3 892 106
US-A- 4 790 147
• PATENT ABSTRACTS OF JAPAN vol. 015, no. 232
(M-1124), 13 June 1991 (1991-06-13) -& JP 03
070960 A (HITACHI LTD), 26 March 1991
(1991-03-26)
(72) Inventor: Takeda, Tsunehiro
EP 1 477 755 B1
Tokyo 135-0044 (JP)
Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent
Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the
Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been
paid. (Art. 99(1) European Patent Convention).
Printed by Jouve, 75001 PARIS (FR)
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Description
[0001] This invention relates to liquid helium circulation
systems and transfer lines used with the said systems.
To be more specific, it relates to the liquid helium circulation system used as part of a brain magnetism measurement system that liquefies helium gas evaporating
from its liquid helium reservoir, where an encephalomagnetometer is disposed in an extreme low temperature
environment, and to the transfer line used with the system
that sends the liquefied helium back to the liquid helium
reservoir. Besides brain magnetism measurement systems, the said liquid helium circulation systems and
transfer lines are also usable with magnetocardiographs
and magnetic resonance imaging (MRI) systems, and in
studying and evaluating the properties of a variety of materials at extreme low temperatures.
[0002] Brain magnetism measurement systems to detect magnetic fields generated by human brains are under development These systems use super-conducting
quantum interference devices (SQUIDs) capable of
measuring brain activities with a high space-time resolution and without harming the organs. The SQUID is
used in the refrigerated state, dipped in the liquid helium
filled in an insulated reservoir.
[0003] With most conventional liquid helium reservoirs
in those systems, the helium gas evaporating from the
reservoir is released into the air. This waste of helium in
large quantity makes the systems economically disadvantageous when helium is as expensive as ¥1,200 per
liter. Moreover, as the liquid helium in the reservoir is
consumed, it has to be replenished with fresh liquid helium from a commercial cylinder. The replenishment however presents problems such that the process is extremely troublesome, or that outsourcing costs are substantial.
[0004] Against the background as above-mentioned,
there are recent moves to develop liquid helium circulation systems, which may recover, recondense and liquefy
the helium gas evaporating from the reservoir in its entirety and send it back to the reservoir.
[0005] Referring to Fig.4, briefly shown below, is the
schematic configuration of a type of such liquid helium
circulation system. 101 stands for a liquid helium reservoir, wherein an encephalomagnetometer is disposed;
102 a drive pump that recovers the helium gas vaporized
inside reservoir 101; 103 a dryer that dehydrates the helium gas recovered; 104 a flow regulating valve; 105 a
purifier; 106 an auxiliary refrigerator; 107 a heat exchanger No.1 for auxiliary refrigerator 106; 108 a condensing
refrigerator and 109 a condensing heat exchanger of condensing refrigerator 108. The helium gas boiling off from
liquid helium reservoir 101 and whose temperature is
raised to about 300° Kelvin (K) is suctioned with drive
pump 102, and sent through dryer 103 and purifier 105
to auxiliary refrigerator 106, where it is cooled down to
about 40° K and liquefied. The liquid helium is sent to
condensing refrigerator 108, where it is further cooled
down to about 4° K as it passes condensing heat ex-
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changer 109. Finally the extreme low temperature liquid
helium is supplied to liquid helium reservoir 101 through
transfer line 110.
[0006] This prototype helium circulation system is basically a system to recover and recycle entirely the helium
gas evaporating from the liquid helium reservoir. Compared with conventional similar systems, whose vaporized helium is released into the air or recovered in a gas
bag or the like for reprocessing, it consumes a remarkably
smaller quantity of helium, promising benefits of economy and efficiency which has been spurring recent efforts
to put to practical use. In addition, the added feature of
the new system demanding little trouble to refill fresh liquid helium would make maintenance of the measurement
system easier as a whole.
[0007] Nevertheless, the new circulation system as
above-mentioned cannot be free from necessary improvements as follows:
[0008] While liquid helium is an indispensable medium
to keep a SQUID in the refrigerated state, a huge amount
of electric energy has to be consumed to run the refrigerator to liquefy helium gas. In addition, a large volume
of water is required to cool the compression pump of the
refrigerator. Furthermore, as the liquefied helium is transferred from the refrigerator to the liquid helium reservoir
through the transfer line, it is difficult to isolate it completely from high-temperature parts, causing a large portion of it to become vaporized, resulting in a poor transfer
rate. Such being the case, the running cost as well as
insulation measures amount to a huge sum comparable
to that in the case of allowing the gas to escape into the
air. An economical version of liquid circulation system
overcoming such problems needs to be developed.
[0009] JP03-070960 which shows the features of the
preamble of claim 1, describes a transfer line having a
liquid helium pipe and helium gas return pipes disposed
in a common vacuum layer in the transfer line.
[0010] US 3,882,687 describes a transfer line having
a central liquid cryogen pipe surrounded by (in increasing
size) a first coaxial pipe containing a two-phase mixture,
a second coaxial pipe which is evacuated, a third coaxial
pipe containing gas and a fourth coaxial pipe which is
evacuated.
[0011] With the above-mentioned considerations in
the background, the inventor has developed the idea of
this invention from the phenomena that the quantity of
heat (sensible heat) required to raise the temperature of
helium gas from about 4° K to about 300° K is much
higher than that (vaporization heat) required for the
phase change from liquid to gas of helium at about 4° K,
and that while the energy required to cool down hightemperature helium to low-temperature helium is moderate, substantial energy is required to liquefy low-temperature helium gas.
[0012] Namely, this invention offers a new type of liquid
helium circulation system as a solution to the problems
conventional circulation systems have had as abovementioned. With this invention, high-temperature helium
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gas as high as 300° K boiling off from the liquid helium
reservoir is recovered, cooled down to about 40° K, a
temperature within the easy reach of a refrigerator, and
supplied to the upper part in said reservoir. Also, lowtemperature helium gas, say about 10° K, near the surface of liquid helium inside said reservoir is recovered
and liquefied at about 4° K and supplied back to said
reservoir. In this manner, the inventory of liquid helium
inside said reservoir is easily replenished by as much as
is lost by evaporation.
[0013] The present invention provides a transfer line
comprising a first line supplying liquid helium, a second
line supplying low-temperature helium gas and a third
line supplying refrigerated helium gas whose temperature is higher than that of said low-temperature helium
gas, characterised in that the first line comprises a pipe
surrounded by a first vacuum layer and the second line
comprises a pipe surrounded by a second vacuum layer
and the third line comprises a pipe surrounded by a third
vacuum layer and in that the first, second and third lines
are disposed in a pipe surrounded by an outer vacuum
layer which surrounds all three lines.
[0014] In a preferred embodiment, the invention provides a transfer line characteristic of its construction consisting of a line that supplies liquid helium, a line that
supplies low-temperature helium gas, and a line that supplies refrigerated helium gas of a temperature higher than
that of said low-temperature helium, with each line surrounded by a vacuum layer and all lines disposed inside
a same conduit whose outer surface is insulated with a
vacuum layer.
[0015] With the liquid helium circulation system described herein, it is possible to minimize liquid helium
boil-off from the liquid helium reservoir because therein
the sensible heat of refrigerated helium gas removes a
large quantity of heat. Also, cooling helium gas from
about 300° K down to about 40° K requires an amount
of energy much less compared with that when producing
liquid helium of about 4° K by liquefying helium gas of
about 40° K. Therefore, compared with conventional systems liquefying the entire volume of helium gas recovered, this system offers outstanding economic benefit by
lowering remarkably the amount of energy consumed in
liquefying helium gas by shortening the running time of
the refrigerator, etc.
[0016] Also, this system recovers and liquefies lowtemperature helium gas in the vicinity of the surface of
liquid helium in the liquid helium reservoir, which greatly
helps save the amount of energy needed in the process
of liquefying helium gas, leading to a large reduction in
running cost.
[0017] An alternative arrangement which does not
form part of the claimed invention provides a transfer line
characteristic of its triple-pipe design consisting of a line
that supplies liquid helium at the center, an intermediate
line that supplies low temperature helium gas, and an
outermost line that supplies refrigerated helium gas of a
temperature higher than that of said low-temperature he-
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lium gas, with each line surrounded by a vacuum layer.
[0018] This system adapts a method for refrigerated
helium gas or low-temperature helium gas to flow around
the line supplying liquid helium liquefied by the refrigerator. This feature is to isolate the line from surrounding
high-temperature parts and protect the liquid helium from
evaporating as it flows though the line, which minimizes
the loss of energy in a helium gas liquefying process and
makes this system a more efficient liquid helium circulation system.
[0019] Preferred embodiments of the invention will
now be described, by way of example only, and with reference to the accompanying drawings in which:
Fig. 1 is a schematic representation of the multi-circulation type liquid helium circulation system suitable for use with this invention. Fig. 2 shows an enlarged side view with a broken section of a transfer
line according to an embodiment of this invention.
Fig. 3(a) shows a cross-sectional drawing of an embodiment of transfer lines according to the invention.
Fig. 3(b) shows an alternative arrangement not forming part of the invention. Fig. 4 shows the schematic
configuration of a conventional circulation type liquid
helium circulation system.
[0020] Referring to Fig. 1 showing a schematic construction of the multi-circulation type liquid helium circulation system for use with this invention, the description
is given of the system as follows:
[0021] Number 1 stands for a liquid helium reservoir
(FRP cryostat) that is disposed inside a magnetic-shield
room and wherein a SQUID is placed. 1a a gas-liquid
separator disposed in said reservoir; 1b a level gauge
measuring the liquid level of liquid helium 13; 1c a pipe
for recovery gas line 12 recovering high-temperature helium gas heated up to about 300° K inside said reservoir.
Number 2 stands for a flow regulating pump that supplies
high-temperature helium gas recovered to a small capacity refrigerator via pipe 1c. 4 a flow regulating valve.
5 a 4 KGM small capacity refrigerator known for its remarkable progress of late. 6 and 7 heat exchangers No.
1 and No.2 of said refrigerator. 6a and 7a No.3 and No.
4 heat exchangers, which liquefy high-temperature helium gas recovered from the reservoir, or fresh helium supplied from a helium cylinder 10 as it is supplied through
line 20 in the event the inventory of liquid helium falls
short inside said reservoir. 8 a 6.5KW helium compressor. 9 a transfer line with combined three lines - 9a that
supplies liquid helium liquefied with refrigerator 5 to liquid
helium reservoir 1; 9b that recovers low-temperature helium gas from inside said reservoir 1 and 9c that supplies
helium gas cooled down to about 40° K with refrigerator
5 to liquid helium reservoir 1. 10 a helium cylinder that
supplements a fresh batch of helium in an emergency.
11 an insert pipe, which is connected with transfer line
11 and disposed in liquid helium reservoir 1. Above-mentioned component units are interconnected with each oth-
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er ensuring fluids to flow in the directions as indicated by
arrows. In addition, 14 forms the magnetic-shield room
of FPR cryostat 1.
[0022] Referring to Figs. 2 and 3, the constructions of
two different types of transfer lines, among others, are
described as follows. Fig.2 is a side view with a broken
section of a transfer line. Fig.3 (a) is the section A-A of
the transfer line in Fig.2 and Fig.3(b) shows a section of
a transfer line of different construction not belonging to
the present invention.
[0023] The example of transfer line given in Fig.3 (a)
has pipe 9a disposed at the center of a surrounding vacuum layer 9d for flowing liquid helium of about 4° K, pipe
9b disposed at the center of a surrounding vacuum layer
9d for flowing low-temperature helium gas of about 10°
K recovered from inside the reservoir and pipe 9c disposed at the center of a surrounding vacuum layer 9d for
flowing refrigerated helium gas cooled down to about 40°
K with the refrigerator. These pipes 9a, 9b and 9c are
lined up in parallel with one another and housed in a large
pipe 9A with a surrounding vacuum layer 9d for insulation
and an insulation material 13 installed in its inside.
[0024] The transfer line according to Fig. 3(b) is a triplepipe version of transfer line 9, consisting of a large pipe
9’c surrounded with a vacuum layer 9d at the outermost,
a medium size pipe 9’b surrounded with a vacuum layer
9d set at the center of pipe 9’c and a small pipe 9’a surrounded with a vacuum layer set at the center of pipe
9’b. This triple-pipe construction is designed to allow the
flow of refrigerated helium gas of about 40° K along the
outer surface of medium size pipe 9’b, low-temperature
helium gas of about 10° K along the outer surface of small
size pipe 9’a and liquid helium of about 4° K through the
inside of small size pipe 9’a.
[0025] In the case of example (a) of transfer line, three
pipes can be bound together, offering an advantage of
smaller outer diameter compared with the triple-pipe construction shown in Fig. 3(b).
[0026] In each case of transfer line 9, the reservoirside end of the transfer line is connected with an insert
pipe 11 disposed in liquid helium reservoir 1, and a gasliquid separator 1a is installed at the end of insert pipe
11. While this gas-liquid separator does not constitute an
essential part of this invention, it is desirable to install it
where it is necessary to prevent the disturbance of temperature equilibrium in the reservoir due to a paucity of
helium gas generating from liquid helium in transit. Of
three pipes placed inside transfer line 9, an end of pipe
9a that supplies the liquid helium liquefied with the refrigerator to liquid helium reservoir 1 is connected with gasliquid separator 1a, an end of pipe 9b that recovers lowtemperature helium gas from inside reservoir 1 and supplies it to the refrigerator is located close to the gas-liquid
separator 1a of insert pipe 11 or in the vicinity of the
surface of liquid helium inside reservoir 1 so that lowtemperature helium gas can be collected from an area
of the lowest available temperature (close to 4° K) inside
reservoir 1, and an end of pipe 9c that supplies refriger-
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ated helium gas, cooled down to 40° K with the refrigerator, to reservoir 1 is opened over insert pipe 11 (the
inner upper part of reservoir 1).
[0027] The function of the liquid helium circulation system with a construction as above-mentioned is as follow:
[0028] The liquid helium pooled inside liquid helium
reservoir 1 starts to gasify at a temperature of about 4°
K inside said reservoir and keeps refrigerating the inner
space of said refrigerator until its temperature rises to a
room temperature of about 300° K by sensible heat. The
high-temperature helium gas of about 300° K is suctioned
out with flow-regulating pump 2 via helium gas recovery
pipe 1c installed at the upper part of reservoir 1. The
entire helium gas recovered is sent to heat exchanger
No. 6 of small-capacity refrigerator 5, where the helium
gas is cooled down to about 40° K The refrigerated helium
is supplied via pipe 9c disposed inside the transfer line
to the upper part inside reservoir 1 and cools down efficiently the inner space of reservoir 1 by sensible heat
until its temperature rises to 300° K While the lower space
inside reservoir 1 is kept at constant 4° K as the liquid
helium inside reservoir 1 evaporates, the evaporation is
slowed down because the shrouding helium gas of about
40° K as above-mentioned inhibits heat infiltration from
above to the liquid helium. Meanwhile, although, in order
to raise the cooling performance of reservoir 1, it is desirable to supply refrigerated helium gas cooled down as
low as possible below about 40° K to the reservoir, it is
economically unfavorable since it demands a system with
a much higher refrigeration capacity.
[0029] Also, pipe 9c with its opening close to the surface of liquid helium inside reservoir 1 recovers low-temperature helium gas of about 40° K, which is liquefied
with the heat exchanger 7 of small capacity refrigerator
5. The liquefied helium is returned to reservoir 1 via pipe
9a inside transfer line 9, and via gas-liquid separator 1a
if necessary. This method of liquefying low-temperature
helium gas of about 10° K using a small capacity refrigerator is instrumental in replenishing constantly the reducing inventory of liquid helium due to evaporation inside said reservoir at a lower energy cost. Moreover, liquefied helium flowing inside transfer line 9 is protected
with refrigerated helium gas or low-temperature helium
gas flowing also inside said transfer line against hightemperature parts, which helps restrict the liquid helium
in transit from evaporating. Meanwhile, liquefying helium
gas of the lowest available temperature drawn out from
inside reservoir 1 helps raise the liquefying efficiency of
refrigerator used, making it possible to use a small capacity refrigerator with an ensuing reduction in running
cost.
[0030] Described above is a transfer line that consists
of pipe 9c that supplies refrigerated helium gas, cooled
down to about 40° K, to reservoir 1, pipe 9b that transports
low-temperature helium gas of about 10° K recovered
from reservoir 1 and pipe 9a that transports liquefied helium. Unlike this design, it is possible to design pipe 9c
that supplies refrigerated helium gas to reservoir 1 as an
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insulated pipe independent from the transfer line.
[0031] Aforementioned is an operational system
where the entire volume of high-temperature helium gas
of about 300° K recovered from reservoir 1 is cooled down
to about 40° K, and the refrigerated helium gas is sent
to the inner upper part of said reservoir. It is also possible,
by operating flow-regulating valve 4, to supply part of
high-temperature helium gas through the line indicated
as 20 in the drawing to the heat exchangers No. 1 6a and
No.2 7a (different from those aforementioned) of refrigerator 5 for liquefying and to return the liquefied helium
to reservoir 1 via aforementioned pipe 9a.
[0032] As above-mentioned, this liquid helium circulation system is designed to perform as follows:
[0033] First, the helium gas whose temperature is
about 300° K from inside the liquid helium reservoir, and
the recovered helium gas is cooled down to about 40° K
in its entirety taking advantage of the first-stage refrigeration cycle of the refrigerator and the refrigerated helium
gas is sent back to the liquid helium reservoir Second,
low-temperature helium gas of about 40° K is recovered
through a pipe with its opening close to the surface of
liquid helium inside the reservoir. The recovered low-temperature helium gas is supplied to the heat exchangers
No. 2 7 of the small capacity refrigerator where the helium
gas is liquefied, and the liquefied helium is returned to
the reservoir to add to the reducing inventory of liquid
helium. Owing to these design features, the helium gas
of 40° K can cool the liquid helium reservoir because a
large quantity of heat is removed as the helium gas is
heated up to about 300° K, and the lower space inside
the reservoir is kept at about 4° K, which makes the system comparable with conventional systems in terms of
cooling effect. Also, the inventory of liquid helium inside
the reservoir is reduced as it evaporates. The design feature to recover and liquefy low-temperature helium gas
in the vicinity of the surface of liquid helium inside the
reservoir and return the liquefied helium into the reservoir
helps minimize energy loss in producing liquid helium,
paving the way for designing a liquid helium circulation
system with high efficiency at a low cost.
[0034] Also, the design feature to have helium gas
cooled down with the refrigerator or low-temperature helium gas recovered from the reservoir protects the liquid
helium liquefied with said refrigerator in transit greatly
helping to reduce the volume of the liquid helium lost by
evaporation.
[0035] Also, while condensing helium gas of about 40°
K to produce liquid helium of about 4° K demands a huge
amount of energy the design feature of this invention to
condense helium gas of about 10° K helps minimize the
liquefying energy, making it possible to use a small capacity refrigerator.
[0036] Meanwhile, it goes without saying that another
type of refrigerator can replace the refrigerator described
above. Using a multi-stage refrigerator would make it
possible to have helium gas of different temperatures
flow at one time. Also, in designing, a controller, though
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it is not shown in the drawing, that is activated with signals
from a sensor such as level gauge disposed inside the
liquid helium reservoir can be included to control the flowregulating valve used in replenishing the inventory of liquid helium. Also, optional component units, materials etc.
are selectable to suit the purpose of the system.
[0037] While the system described above uses one
unit of small capacity refrigerator for producing liquid helium and refrigerated helium gas, instead, it is possible
to use two or more units of smaller capacity refrigerators,
each one assigned with a specific function. Furthermore,
while the temperature of helium gas supplied to the refrigerator of the system described above for refrigeration
is about 40° K, this temperature is not binding and helium
gas at a variety of temperatures may be used depending
upon the purpose of the work.
[0038] Because of its design feature of recovering lowtemperature helium (about 10° K) by means of a pipe
with its opening close to the liquid helium inside the reservoir, liquefying the recovered gas with a small capacity
refrigerator and returning the liquefied helium to said reservoir to replenish the inventory of liquid helium, the loss
of energy in producing liquid helium can be minimized,
paving the way for designing highly efficient liquid helium
circulation systems operating at a low running cost.
[0039] Its design feature ensuring the effective use of
a large quantity of sensible heat required while helium
gas of about 40° K is raised to 300° K for cooling the
liquid helium circulation system dismisses the conventional need of liquefying the entire volume of helium gas
with ensuing benefits of saving measurable energy and
running cost.
[0040] Its design feature to recover and recycle helium
in its entirety dismisses the conventional method of troublesome helium replenishment and reduces largely the
cost involving liquid helium.
[0041] Its feature to transport the liquid helium liquefied
with the refrigerator without allowing it to contact hightemperature parts prevents it from evaporating while in
transit and ensures its stabilized return to the reservoir.
Claims
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1.
A transfer line comprising a first line (9a) for supplying liquid helium, a second line (9b) for supplying
low-temperature helium gas and a third line (9c) for
supplying refrigerated helium gas whose temperature is higher than that of said low-temperature helium gas, characterised in that the first line comprises a pipe (9a) surrounded by a first vacuum layer
(9d) and the second line comprises a pipe (9b) surrounded by a second vacuum layer (9d) and the third
line comprises a pipe (9c) surrounded by a third vacuum layer (9d) and in that the first, second and third
lines are disposed in a pipe surrounded by an outer
vacuum layer (9d).
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A transfer line as claimed in claim 1, wherein the first,
second and third lines (9a, 9b, 9c) are disposed in
parallel.
A transfer line as claimed in claim 1 or 2, wherein
the first, second and third lines (9a, 9b, 9c) are disposed in an insulating material (13) and the outer
vacuum layer (9d) surrounds the insulating material
(13).
ne (9d).
Patentansprüche
Übertragungsleitung umfassend eine erste Leitung
(9a) zum Zuleiten flüssigen Heliums, eine zweite Leitung (9b) zum Zuleiten von Heliumgas tiefer Temperatur und eine dritte Leitung (9c) zum Zuleiten gekühlten Heliumgases, dessen Temperatur höher ist
als diejenige des Heliumgases niedriger Temperatur, dadurch gekennzeichnet, dass die erste Leitung ein Rohr (9a) umfasst, welches von einer ersten
Vakuumschicht (9d) umgeben ist, und dass die zweite Leitung ein Rohr (9b) umfasst, welches von einer
zweiten Vakuumschicht (9d) umgeben ist, und dass
die dritte Leitung ein Rohr (9c) umfasst, welches von
einer dritten Vakuumschicht (9d) umgeben ist, und
dass die erste, zweite und dritte Leitung in einem
Rohr angeordnet sind, welches von einer äußeren
Vakuumschicht (9d) umgeben ist.
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2.
Übertragungsleitung gemäß Anspruch 1, wobei die
erste, zweite und dritte Leitung (9a, 9b, 9c) parallel
angeordnet sind.
3.
Übertragungsleitung gemäß Anspruch 1 oder 2, wobei die erste, zweite und dritte Leitung (9a, 9b, 9c)
in einem Isoliermaterial (13) angeordnet sind, und
die äußere Vakuumschicht (9d) das Isoliermaterial
(13) umgibt.
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Revendications
1.
Conduite de transfert comprenant une première conduite (9a) pour fournir de l’hélium liquide, une deuxième conduite (9b) pour fournir de l’hélium gazeux à
basse température et une troisième conduite (9c)
pour fournir de l’hélium gazeux réfrigéré dont la température est supérieure à celle dudit hélium gazeux
à basse température, caractérisée en ce que la
première conduite comprend un tube (9a) entouré
d’une première couche sous vide (9d) et la deuxième
conduite comprend un tube (9b) entouré d’une
deuxième couche sous vide (9d) et la troisième conduite comprend un tube (9c) entouré d’une troisième
couche sous vide (9d) et en ce que les première,
deuxième et troisième conduites sont disposées
dans un tube entouré d’une couche sous vide exter-
2.
Conduite de transfert selon la revendication 1, dans
laquelle les première, deuxième et troisième conduites (9a, 9b, 9c) sont disposées parallèlement.
3.
Conduite de transfert selon la revendication 1 ou 2,
dans laquelle les première, deuxième et troisième
conduites (9a, 9b, 9c) sont disposées dans un matériau isolant (13) et la couche sous vide externe (9d)
entoure le matériau isolant (13).
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REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European
patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be
excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description
•
JP 3070960 A [0009]
•
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US 3882687 A [0010]